Scavenge systems for a gas turbine engine including a valve positioned at a first drainage outlet of an enclosure to selectively open and evacuate liquid from the cavity through the first drainage outlet in response to the valve being submerged in liquid are provided. Methods of reducing suction of air from an enclosure of a cavity of a gas turbine engine are further provided.

A four-stroke engine lubrication system comprises: an engine body in which a crank shaft chamber and an air valve distribution chamber are arranged; a cylinder head cover fixed onto the engine and communicated with the atmosphere; and an oil storage tank which is configured to store lubricating oil, arranged on the engine body, located at one side of a cam, and provided with an oil mist generation device therein, wherein an oil outlet passage of the oil mist generation device communicates the oil storage tank with the crank shaft chamber via an oil outlet pipe; the crank shaft chamber is communicated with the air valve distribution chamber via a check valve; the air valve distribution chamber is communicated with the oil storage tank via a pipe; the air valve distribution chamber is communicated with the cylinder head cover; and the cylinder head cover is communicated with the oil storage tank.

In a general-purpose engine including a cylinder block extending obliquely from one side of a crank case, and a cylinder head connected to an end surface of the cylinder block via a gasket, a unidirectional valve for allowing a flow of a fluid from a crank chamber to a valve operating chamber and blocking a reverse flow of the fluid is installed in an upper oil passage. In a case where lubricant oil reserved in the crank chamber flows into the valve operating chamber via a lower oil passage when the engine inclines such that the inclined cylinder block further slants, positive pressures transmitted from the crank chamber to the valve operating chamber push the oil, which once flows into the valve operating chamber, back to the crank chamber via the lower oil passage.

Scavenge systems for a gas turbine engine including a valve positioned at a first drainage outlet of an enclosure to selectively open and evacuate liquid from the cavity through the first drainage outlet in response to the valve being submerged in liquid are provided. Methods of reducing suction of air from an enclosure of a cavity of a gas turbine engine are further provided.